The present invention relates to a lamp unit comprising a fluorescent tube with electrodes having wire leads extending therefrom, a lamp base to which the leads are connected, and a ballast housing betwen the tube and the base. The housing has a forward end toward the lamp base, and a circumferential wall extending therebetween. The wall at least partially defines a primary cavity having therein an inductive stabilization ballast through which at least one of the leads is wired.
U.S. Pat. No. 4,353,007 describes a lamp unit of the above described type, the housing having an integral shell portion which converges toward the rearward end and a floor portion between the ends to support the ballast. The ballast is situated in the primary cavity with a circumferential space between it and the circumferential wall, in which space the wire leads are located for connection to the ballast, the base, or a starter located in the shell portion. The primary cavity is completely open toward the forward end to receive the leads.
The prior art lamp unit requires that the wire leads be insulated in order to prevent short circuiting. Since the forward end of the housing is open, the discharge tube extends into the primary cavity and thus is not thermally isolated from the ballast. Further, the circumferential space around the ballast acts as an insulator.